With the growing demand for communications systems capable of transmitting increasing amounts of information, optical communication systems have gained in prominence, and have become a standard for telecommunications. Such systems have typically utilized wavelength division multiplexing (“WDM”) or time division multiplexing (“TDM”) techniques.
Communications systems that use TDM techniques utilize the allocation of successive time segments of a stream of continuous data transmitted by the systems for separate carrier signals. In such TDM communications systems, the separate carrier signals are sampled at predetermined intervals and for a predetermined duration. The samples of the separate carrier signals are then combined or “multiplexed” and transmitted in succession over a transmission link of the TDM system, which is typically an optical fiber. After transmission through the TDM system, the samples corresponding to the individual carrier signals are separated or “demultiplexed” and then the carrier signals are recovered. Communications systems that use WDM techniques differ from TDM systems in that they utilize the simultaneous transmission of carrier signals of different discrete frequencies.
To illustrate, for a TDM system transmitting four carrier signals, a time slot having a set duration would be determined for the system, typically by taking into consideration various equipment-related parameters of the system. Samples would be taken of each of the four carrier signals, with each sample having a duration that is equal to or less than the predetermined time slot duration. These samples would then be combined and transmitted sequentially over a fiber optic transmission line, with every fourth time slot of the predetermined duration being allotted to a sample of one of the four separate carrier signals.
With the growing applicability of optical communications systems, particularly TDM systems, there has been a concurrent increase in demand for optical pulse generators capable of increasingly rapid repetition rates. Presently optical pulse generators with repetition rates in the GigaHertz (GHz) range are known. Optical pulse generators with repetition rates of a few TeraHertz (THz) are also known.
While some optical pulse generators have been realized in the prior art, none are known to have been capable of producing optical pulses with repetition rates of hundreds of THz. For example, an Ultrashort-Pulse Source with Controllable Multiple-Wavelength Output is described in U.S. Patent Application Publication No. US2002/0034199A1. This disclosure is concerned with the wavelength conversion of pulses from an ultrashort-pulse laser producing pulses in the femtosecond (fs) to picosecond (ps) regime. The pulses produced by the ultrashort-pulse laser are then converted to one or more different wavelengths by means of optical parametric generation in integrated waveguides. These converted pulses are not more rapid or frequent than the pulses produced by the ultrashort-pulse laser, and consequently no improvement in repetition rate over the prior art is disclosed.